Liners are commonly used to repair and/or reinforce ruptured or weak areas in pipeline networks such as sewer systems and the like. Lateral pipes i.e. those extending from a main pipe, are especially susceptible to damage and have traditionally been repaired by conventional excavation methods. As will be appreciated, excavation methods are expensive, time consuming and disruptive.
To avoid the problems associated with excavation methods, “cure-in-place” pipeline repair technology has been developed to allow pipelines to be repaired without requiring disruptive excavation. During “cure-in-place” pipeline repair, a resin impregnated liner is delivered to the pipeline section to be repaired and is maintained in place at that location until the curing process is complete.
A variety of installation systems for delivering “cure-in-place” liners to pipeline sections to be repaired are used in the industry. For example, the liner may be pushed along the pipeline to its desired location by means of a series of push-rods. As will be appreciated, transitional areas along the pipeline such as bends and/or fittings create significant delivery problems as the push-rods are unable to effectively move beyond these transitional areas. Alternatively, and more commonly used in the industry, the liner may be pulled along the pipeline to its desired location using a winch and cable. U.S. Pat. No. 6,691,741 to Manners shows a pull-in liner delivery method wherein an inflatable bladder/resin impregnated felt liner assembly is pulled into the pipeline to repair a damaged pipeline section. Inversion delivery where a liner is unrolled through itself by applied pressure as it projects forwardly into a pipeline has also been considered. U.S. Pat. No. 4,366,012 to Wood shows an inversion delivery process wherein a felt liner, impregnated with uncured resin is inverted into a pipeline in need of repair.
The installation of resin-impregnated liners in pipelines presents certain challenges. For both push-in and pull-in delivery methods, excessive friction during positioning of the liner imparts longitudinal stresses on the liner, often resulting in stretching of the liner. This stretching is undesirable as it may result in weak regions of lined pipeline, and increase the likelihood of future failure of the repaired pipeline section. With respect to inversion delivery methods, due to the considerable pressures used to unroll the liner, liner rupture is not uncommon. This rupture problem is more prevalent when installing longer liners as greater pressures are required during liner installation.
Pipelines containing bends (i.e. 22°, 45°, 90°) and/or other fittings (i.e. Y- and T-junctions) present additional challenges. As practitioners in the industry are aware, liners delivered by prior art installation systems are generally prone to creasing in these areas of transition. Creases disrupt fluid flow and may initiate an obstruction in the pipeline. Proper installation of the liners requires the liners to be smoothly and evenly urged into contact against the inner surface of the pipeline to be repaired. Conventional PVC/vinyl inflatable bladders used in prior art installation systems to urge liners into contact with the inner surface of the pipeline in transitional areas have been found to be deficient due to the nonmalleable nature of these inflatable bladders. As a result, these inflatable bladders often introduce folds and/or creases into the liners in these transitional areas. There is clearly a need for an improved liner assembly that can accommodate a wide variety of pipeline configurations.
It is therefore an object of the present invention to obviate or mitigate at least one of the above described disadvantages.